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Hacking the thylakoid proton motive force for improved photosynthesis: modulating ion flux rates that control proton motive force partitioning into Δψ and ΔpH.

Authors
  • Davis, Geoffry A1, 2
  • Rutherford, A William3
  • Kramer, David M4, 5
  • 1 Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA.
  • 2 Cell and Molecular Biology Graduate Program, Michigan State University, East Lansing, MI 48824, USA.
  • 3 Department of Life Sciences, Imperial College London, London SW7 2AZ, UK.
  • 4 Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, MI 48824, USA [email protected]
  • 5 Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA.
Type
Published Article
Journal
Philosophical Transactions of The Royal Society B Biological Sciences
Publisher
The Royal Society
Publication Date
Sep 26, 2017
Volume
372
Issue
1730
Identifiers
DOI: 10.1098/rstb.2016.0381
PMID: 28808100
Source
Medline
Keywords
Language
English
License
Unknown

Abstract

There is considerable interest in improving plant productivity by altering the dynamic responses of photosynthesis in tune with natural conditions. This is exemplified by the 'energy-dependent' form of non-photochemical quenching (qE), the formation and decay of which can be considerably slower than natural light fluctuations, limiting photochemical yield. In addition, we recently reported that rapidly fluctuating light can produce field recombination-induced photodamage (FRIP), where large spikes in electric field across the thylakoid membrane (Δψ) induce photosystem II recombination reactions that produce damaging singlet oxygen (1O2). Both qE and FRIP are directly linked to the thylakoid proton motive force (pmf), and in particular, the slow kinetics of partitioning pmf into its ΔpH and Δψ components. Using a series of computational simulations, we explored the possibility of 'hacking' pmf partitioning as a target for improving photosynthesis. Under a range of illumination conditions, increasing the rate of counter-ion fluxes across the thylakoid membrane should lead to more rapid dissipation of Δψ and formation of ΔpH. This would result in increased rates for the formation and decay of qE while resulting in a more rapid decline in the amplitudes of Δψ-spikes and decreasing 1O2 production. These results suggest that ion fluxes may be a viable target for plant breeding or engineering. However, these changes also induce transient, but substantial mismatches in the ATP : NADPH output ratio as well as in the osmotic balance between the lumen and stroma, either of which may explain why evolution has not already accelerated thylakoid ion fluxes. Overall, though the model is simplified, it recapitulates many of the responses seen in vivo, while spotlighting critical aspects of the complex interactions between pmf components and photosynthetic processes. By making the programme available, we hope to enable the community of photosynthesis researchers to further explore and test specific hypotheses.This article is part of the themed issue 'Enhancing photosynthesis in crop plants: targets for improvement'. © 2017 The Author(s).

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